Field of the Invention
The present invention relates to an imaging apparatus, a method of driving the same, and an imaging system.
Description of the Related Art
The imaging apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-143078 includes vertical signal lines and charge integrating amplifiers for respective pixel columns. Image signals readout from each pixel column via the vertical signal line and the charge integrating amplifier are output to a plurality of horizontal signal lines. The charge integrating amplifier is controlled to be in an ON state or a standby state by a horizontal scanning circuit. In Japanese Patent Application Laid-Open No. 2005-143078, it is disclosed that, with such configuration, in a period in which readout is not performed, the charge integrating amplifier may be switched to the standby state to reduce current consumption. According to the operation timing chart of the solid imaging apparatus in Japanese Patent Application Laid-Open No. 2005-143078, with the elapse of time, the number of operating charge integrating amplifiers is increased, and after becoming the same as the number of horizontal signal lines, the number of operating charge integrating amplifiers becomes constant.
However, when the number of operating charge integrating amplifiers is changed, currents supplied from a power source to the charge integrating amplifiers vary. At this time, waveforms of power supply voltages applied to the imaging apparatus may vary with time. This gives rise to a possibility that output voltages of a pixel circuit may vary. In a case where image signals are read while the output voltages of the pixel circuit vary due to such cause, deteriorated image signals may be read, and image quality may be deteriorated.